Case 7- infection clinical Flashcards
Rhinovirus
Causes 80% of colds, grows in the nasal cavities and upper respiratory tract. Lots of different serotypes. Several serotypes circulate simultaneously for several years then they are displaced so we are unable to develop resistance. It is transmitted through the respiratory route so air droplets, contaminated surfaces and hand to mouth.
Adenovirus
Causes by non-enveloped double stranded DNA viruses. It was first isolated from human adenoids. It is responsible for 5-10% of respiratory viral infections. 51 different serotypes which have been classified into 7 species (A-G). Outbreaks in densely populated areas with a high population such as barracks and hostels.
Adenovirus symptoms
Cold like symptom, Pharyngitis, Bronchitis, Pneumonia, Diarrhoea, Fever and Pink eye
Adenovirus vaccine
There is vaccination in new military recruits to reduce outbreaks of infection
Diagnosing Adenovirus
PCR. Virus isolation from clinical samples, immunological techniques will allow you to identify the specific subtype of the adenovirus.
Coronavirus
Coronaviruses are enveloped, single stranded RNA viruses. Two strains cause between 2-10% of common cold cases, normally mild infections. There is an incubation period of three days before symptoms show.
Coronavirus symptoms
Malaise, nasal discharge, no fever, sore throat
SARS
SARS originated from a reservoir Rat/Civet cat. It spread throughout South-East Asia, the epicentre was Hong Kong. There have been no cases since 2004. Contained by public health measures. It also spread to Canada as there is lots of travel between HK and Canada.
Diagnosing coronavirus
Through RT-PCR (reverse transcriptase) from swabs
MERS
Originated in the middle east, majority of cases are in saudi arabia
Paramoxyvirus
It is a respiratory syncytial virus (RSV) which is the most common causative agent of bronchiolitis in infants. Paramyxovirus is an enveloped, single-stranded RNA virus. It may cause death in the very young, elderly and immune-compressed. Peaks in the winter.
Paramoxyvirus (measles, mumps) symptoms
Incubation period of 5 days, the illness is similar to the common cold (in most cases). Some children under a year old will show signs of pneumonia/bronchiolitis. Re-infection is common. 90% of infants get infected by 2. Only affects infants
Paramoxyvirus diagnosis
Antigen testing/ cell culture/ RT-PCR
RSV prevention
Palivizumab monoclonal antibodies are given prophylactically to susceptible infants, using effective hand hygiene.
What does influenzas cause
Regular pandemics and epidemics. You get a lot of variation year on year
Influenza virus
Influenza virus are orthomyxoviruses, this means that they are enveloped negative RNA viruses with segmented genomes. The transmission is via the respiratory route, there is a 2-3 day incubation period before you see any symptoms. The virus replicates in epithelial cells of the respiratory tract, the cilia are destroyed. Short lived disease
Influenza symptoms
Abrupt onset, Shivering, Malaise, Headache, Aching limbs and back, High fever (39 degrees). Many of the symptoms are due to the cytokine storm released by infected cells.
When is infleunza dangerous
Potentially dangerous for the very young/elderly. Can be associated with secondary infections like pneumonia
Influenza virus structure
The Genome is composed of 8 x RNA segments which are surrounded by matrix proteins. On the genome is NP proteins. On the surface of the virus you have the Neuraminidase (N) proteins. The Neuraminidase is antigenic and aids release from infected cells, so it can invade other cells. Another surface protein they have is Haemagglutinin (H), it is antigenic and binds to target cell surfaces.
What defines the 3 influenza types
By the serology of the internal matrix-proteins and N-proteins
Influenza A
Linked to epidemics and pandemics. It infects animals (pigs and birds). Major changes in these antigens can occur, this is dangerous as there may not be widespread immunity to this variation.
How you classify influenza A
It is categorised based on the antigenic relationship of external spike proteins e,g., H1NI and H5N1. There are 7 different types of H-Haemagglutinin (H1-H7). There are 9 different types of N-Neuraminidase (N1-N9).
Influenza B
Causes milder epidemics
Why does flu give rise to pandemics?
Influenza experiences genetic variability that gives rise to antigenic changes that evade previous immunity
Antigenic drift
Minor changes in H and N proteins due to random mutations/substitutions. This because virus replication is not tightly controlled so errors happen regularly. After 4 years you will no longer have immunity to the virus due to the accumulation of mutations from drift variants. Results in influenza A and B epidemics
Antigenic shift
When the influenza A virus acquires new H and N proteins. As the change is so abrupt people quickly loose their immunity and it can result in Influenza A pandemics. This occurs every 10-20 years i.e. Swine flu.
How does antigenic shift arise?
Antigenic shift occurs when two different flu viruses infect the same cell and genetic re-assortment occurs. The net result is a new virus with different H and N proteins. This can happen in birds or pigs and then be transferred to humans. Genetic segments can jump from cell to cell and between different species to create a completely different virus. Pandemics outbreaks of flu occur after the emergence of shifted strains.
Influenza treatment
Neuraminidase inhibitors like Tamiflu (oseltamivir) and Relenza (zanmivir). Only used in high risk groups as its not very effective but is expensive.
Influenza vaccination
For children it’s a live vaccine given nasally. For adults they mainly use inactivated vaccines containing purified H and N subunits. It is re-formulated at intervals to match prevalent strain. Its about 30-60% effective in adults, also reduces complications.
Endemic
A disease that is always prevalent in certain population or region, i.e. Malaria in the topics
Epidemic
An outbreak of a contagious disease that spreads rapidly and widely
Pandemic
An epidemic over a wide geographic area and affecting a large proportion of the population, i.e. COVID-19
Spanish flu
1918-1920
H1N1
50 million deaths
Asian flu
1957-58
H2N2
1-4 million deaths
Hong kong flu
1968-69
H3N2
33,000 deaths
Swine flu
2009-2010
New H1N1
19,000 deaths
Bird flu/avian flu
H7N9
Types of upper RTI’s
Common cold, Sinusitis, Tonsillitis and Laryngitis
Types of lower RTI’s
Bronchitis, Bronchiolitis, Chest infection and Pneumoniae
FeverPAIN scores
Determines if someone has Strep Pharyngitis. Score 1 point for each:
FEVER over 38 degrees
Purulence (pharyngeal / tonsillitis exudate)
Attend rapidly (3 days or less)
Severely inflamed tonsils
No cough or coryza
